yields an object that displays as the unevaluated form of expr, but that is evaluated if it is explicitly given as Mathematica input.
- Defer[expr] returns an object that remains unchanged until it is explicitly supplied as Mathematica input and evaluated using Shift+Enter, Evaluate in Place, etc.
- Defer gives an object whose evaluation is merely deferred until it is explicitly given as Mathematica input; HoldForm gives an object that is never evaluated.
- If an object contains several levels of nested Defer constructs, one level is removed each time the object is evaluated as Mathematica input.
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